1. Field of the Invention
The present invention is generally in the field of electrical circuits. More particularly, the present invention relates to low noise bias voltage and current generation.
2. Background Art
Microphones are used in electronic devices to convert sound into electrical signals. The electrical signals outputted by a typical microphone are weak and represented by small voltage or current variations. As such, a stable and low noise microphone bias voltage or current is needed to properly operate a typical microphone. Moreover, different types of microphones and different chips interfacing with the different microphones, e.g. different audio processing or base band integrated circuits (ICs), create an environment in which there is a great need for flexibility to accommodate different voltage and current levels for the different audio processing or base band ICs and the different microphones, while all such different voltage and current biases need to be stable and low noise.
According to conventional techniques, a separate bias generation IC, apart from the chip (e.g. an audio processor or a base band processor) that processes the electrical signals generated by a microphone, is employed to provide a stable and low noise voltage or current bias for the microphone. Moreover, it is presently difficult to easily introduce the numerous precise voltage or current bias conditions required for different types of microphones and for the different types of ICs receiving electrical signals from the microphones. The conventional approach requires modifications to bias generation ICs that are fabricated separately from the audio processing and base band ICs that receive electrical signals from the biased microphones. Inherent in the conventional approach is the increased component count, i.e. the separate bias generation IC, and also the lack of flexibility of the separate bias generation IC to accommodate different microphones and different audio processing or base band ICs.